Coherent bisection of 141 THz using sum frequency generation of 1064 and 709 nm radiation

The frequency interval (141 THz) that exists between 1064 nm radiation and the unusual semiconductor wavelength of 709 nm has been coherently divided by using an optical phase-locked loop to control a slave laser lying at the mean frequency of these two wavelengths. The 709 nm radiation has been generated by a combination of wavelength tuning in an extended cavity and temperature tuning of a ridge-waveguide semiconductor laser with a nominal wavelength of 728 nm. Two nonlinear processes have been used to produce the coherent division: the sum frequency mixing of 1064 and 709 nm radiation to produce 425 nm radiation and the second harmonic generation of 851 nm light to produce the same wavelength radiation.     

Frequency tuning and doubling in Yb-doped fiber lasers

A compact Yb-doped fiber laser (YDFL) based on a tunable fiber Bragg grating (FBG) with ～6 W output power and ～45 nm tuning around 1080 nm has been developed. The laser output power and its spectral width (～0.15 nm) do not change significantly at the tuning, while the FBG reflection coefficient increases with an increase in FBG compression. It has been shown that this increase is due to stress-induced changes in the FBG’s refractive-index modulation amplitude. Intracavity frequency doubling in the YDFL has also been performed. About 0.4 W of green radiation with tuning in the range 540–548 nm has been achieved with a KTP nonlinear crystal.     

紫外双光栅光谱仪结构设计与波长精度分析

为了满足太阳光谱在170～380 nm波段的精确观测需求,设计了波长重复性精度优于±0.02 nm的紫外双光栅光谱仪。波长扫描机构是双光栅光谱仪的关键组件,根据凹面光栅色散原理,将光学设计指标转换为波长扫描机构设计的输入参数,分析了影响光谱仪波长重复性精度的误差源。根据分析结果得知,丝杠的重复定位误差是影响波长重复性的主要误差源。选用重复定位精度为±2μm的丝杠设计了波长扫描机构,并对光谱仪整机进行了设计。以汞灯光源对光谱仪的波长重复性指标进行了验证实验。实验结果表明,设计的光谱仪波长重复性介于-0.005～+0.007 nm之间,满足波长重复性优于±0.02 nm的指标要求。     

一种五波长半导体激光生物组织辐照仪

采用GaAlAs单量子阱半导体激光器和LD泵浦的Nd:YVO4－KTP倍频激光器等研制了国内首台可从光导纤维输出5种波长的半导体激光生物组织辐照仪,该仪器已在激光生物医学领域投入应用．     

Wideband Antireflection Film Fabricated by Glancing Angle Deposition

Graded-index ZrO2 films has been fabricated on K9 glass by glancing angle deposition. Because the index mismatch at the interface has been reduced, the film results in wideband high-transmission antireflection. From 400nm to 1200nm, the film reflection is lower than 0.8% and the lowest value is 0.2% at 432nm.     

氢在碳纳米纤维中的低温吸附储存特性

利用容积法测量了77K下氢在一种碳纳米纤维上的吸附等温线。采用分子模拟的方法模拟了77K下氢分子在平板状碳纳米纤维中的吸附,碳纳米纤维的石墨层层间距分别为0.335nm、0.6nm、0.9nm以及1.5nm。模拟结果表明:石墨层层间距为0.335nm的碳纳米纤维在77K下吸附储氢密度很难达到DOE的能量密度标准;当板间距为0.9nm时,系统吸附储氢的重量密度和体积密度均能达到最大,且在77K、1MPa下,能达到DOE的能量密度标准。     

利用光栅光谱仪研究乙醇汽油溶液的吸收特性

利用WGD-8A型多功能光栅光谱仪测量了不同汽油体积含量的乙醇汽油溶液对波长为300.0～430.0 nm光的吸收光谱,分析了乙醇汽油吸光度和汽油浓度的关系,在稀溶液吸光度的朗伯-比尔定律基础上,进一步研究了2种高浓度混合溶液吸光度的计算方法,并得出了入射光波长为377.0,382.0,391.5,410.9 nm时乙醇汽油的吸光度与汽油体积浓度的关系式.     

Mid-infrared supercontinuum generation in soft-glass suspended core photonic crystal fiber

Supercontinuum from 800 to 2,600 nm has been obtained in a soft glass suspended-core photonic crystal fiber. The fiber has been fabricated using an in-house synthesized, lead-bismuth-galate oxide glass (PBG-08), which has a transmission window from 500 nm to 4,500 nm. Dispersion characteristic has been designed to enable efficient pumping in the anomalous regime, using typical telecommunication wavelengths and influence of discrepancy between design and physical dispersion profile of fiber is discussed. An optical parametric amplifier system seeded with a Ti:Sapphire oscillator has been used as a light source (70 fs pulses with 100 kHz repetition rate). Supercontinuum bandwidth on the mid-infrared side is limited by OH $^-$ absorption of the glass and presence of second zero-dispersion wavelength in the spectral area of interest. Flatness the spectrum remains under 7 dB from roughly 1,800 nm to about 2,500 nm.     

Determination of the Partial Pressure of Thallium in High-Pressure Lamp Arcs: A Comparative Study

The partial pressure of thallium in high-pressure Hg-TlI discharges with different mercury, thallium, and electron pressures has been measured by using the optically thin line Tl 655 nm and the self-reversed line Tl 535 nm. The partial pressure at the arc axis has been measured from the line Tl 655 nm. The effective partial pressure has been measured from the self-reversed line Tl 535 nm on the basis of the multiparameter method, and it has been calculated from the known axis pressure of thallium and the calculation of its radial variation by taking into account the chemical reactions. The experimental results confirm the dispersion character of the blue wing of the line Tl 535 nm. The systematic difference obtained between the measured and calculated effective pressure, particularly at the moment of minimum electron density, may be interpreted by deviations from the local thermodynamic equilibrium (LTE) caused by overpopulation of the upper level of the line Tl 535 nm.     

氯化稀土(Eu3+,Tb3+)乙酰丙氨酸咪唑的FTIR光谱和激光激发光谱

用OPO激光为激发光源,对两种新型三元固态配合物氯化稀土(Eu3+,Tb3+)乙酰丙氨酸咪唑进行了荧光光谱测试,发现激光激发波长为487 nm时,铽配合物在545 nm处产生较强的铽(Ⅲ)离子特征绿色荧光谱线,激发波长为465 nm和525 nm时,铕配合物均在613 nm和618 nm处产生强的铕(Ⅲ)离子特征红色荧光谱线;并且这两种稀土配合物的荧光均比相应稀土盐的强.分析了上述现象产生的原因,讨论了配体对中心离子发光性能的影响.同时还测试了标题配合物的FTIR和UV/VIS光谱.     

Wavelength dependent resonant nonlinearities in a standard saturable absorber IR26 on picosecond time scale

Nonlinear optical properties of a standard dye IR26 have been studied by using the Z-scan technique to decipher the difference in the mechanism of nonlinear absorption on picosecond time scale at two wavelengths i.e. at 1064 nm and 532 nm. A prominent contribution of nonlinear absorption is observed in the Z-scan profiles at 1064 nm. The dye exhibits the mechanism of self-defocusing at 1064 nm in contrast to that of self-focusing at 532 nm. While the two photon absorption has been found to be the dominant mechanism of reverse saturable absorption at 1064 nm, the mechanism of excited state absorption is operating at 532 nm. Additionally, the optical phase conjugate geometry of degenerate four wave mixing (DFWM) technique has been used to measure the third order nonlinear susceptibility values at 532 nm to compare with those obtained from the Z-scan profiles.     

A tunable,frequency-doubled,continuous-wave dye laser using ADA

A tunable, continuous-wave, frequency-doubled, rhodamine 6G dye laser has been developed using an ADA crystal placed in an astigmatic and coma compensated cavity. Generated UV powers of the order of 30mW cw in a single direction in gaussian form over the range 292–302 nm have been obtained by temperature phase matching, and with a 4.5 W pump. Power output is affected by thermal phase mismatching, and is ultimately limited by thermal lensing. Two scanning systems have been developed; a broadband arrangement of linewidth 0.02 nm continuously tunable over a range of 2 nm, and a narrowband system of linewidth 0.002 nm continuously tunable over a range of 1 nm. The laser has been used to detect the Rydberg states of Rb up to a principal quantum of n = 74.     

Diode-pumped Nd:YAG laser emitting at 899 nm and below

We present what is, to the best of our knowledge, the first diode-pumped Nd:YAG laser emitting at 899 nm and below, based on the (4)F(3/2) - (4)I(9/2) transition, generally used for a 946 nm emission. A power of 630 mW at 899 nm has been achieved in cw operation and 16 mW at 884 nm with a fiber-coupled laser diode emitting 9 W at 808 nm. Intracavity second-harmonic generation in cw mode has also been demonstrated with a power of 100 mW at 450 nm by using a LiB(3)O(5) nonlinear crystal.     

Diode end-pumped high-efficiency Nd:YAG laser

A close-coupled scheme has been developed to end-pump the Nd:YAG rod using diode lasers tuned to 808 nm. By using a single diode laser, an optical-to-optical conversion efficiency of about 40% has been demonstrated in the multimode operation at 1064 nm.     

Electric-field mediated nickel-induced nanocrystallization of?amorphous silicon thin films in the complete absence of external heating

DC electric-field mediated nanocrystallization of thermally evaporated silicon thin films with nickel as seed/cap layer has been attempted in complete absence of any external heat input. When 60 nm Si thin film coated onto 5 nm Ni thin film was treated by a direct current (DC) electric field (up to 3.3 kV/cm up to 5 minutes) after the deposition, amorphous silicon thin films became nanocrystalline (6–10 nm). Silicon nanograins (average diameter 90 nm) grow to larger sizes (average diameter 240 nm) with sharpening of grain size distribution. Huge grain growth (4-fold increase) has been observed when nickel was used as cap layer (5 nm Ni/60 nm Si). XRD data show the signature of nickel silicide formation on the surface in nickel cap layer case. Field treatment has changed the optical absorption edge (shifts left in nm units) and the refractive index of silicon thin film when nickel was used as under layer, and an almost negligible effect on the optical properties has been observed when nickel was used as cap layer.     

基于光纤光栅的可调谐半导体激光器

本文利用光纤光栅(FBG)形成外腔反馈及F-P半导体激光器的多模特性,得到波长稳定、可调谐的半导体激光光源,系统研究了不同反馈比率对激光器光谱特性的影响.通过向FBG施加轴向拉力和压力可实现10nm的波长调谐,得到一系列波长间隔0.94nm的激光输出,边模抑制比达35dB,光谱线宽小于0.2nm.     

Dual mode emission and harmonic generation in ZnO-CaO-Al2O3: Er nano-composite

Er³⁺ doped ZnO-CaO-Al₂O₃ nano-composite phosphor has been synthesized through combustion method and its emission and harmonic generation properties have been studied. The X-ray diffraction and thermal analysis techniques have been used to prove the dual phase (ZnO and CaO-Al₂O₃) nature of the phosphor. The phosphor has shown up-conversion emission on near-infra-red (976 nm) excitation and down-conversion emission on 355 nm excitation in presence of Er³⁺ and thus behaves as a dual mode phosphor. On excitation with 976 nm diode laser, material shows color tunability (calcination of composite material at different temperatures). Formation of ZnO nanocrystals on heat treatment of as-synthesized sample has shown its characteristic emission at 388 nm and also the energy transfer from ZnO to Er³⁺ ions. The low temperature emission measurements have been carried out and the results have been discussed. Phosphor has shown strong second harmonic generation (SHG) at 532 nm on 1064 nm and at 266 nm on 532 nm excitation.     

Solid-state dye lasers based on copolymers of 2-hydroxyethyl methacrylate and methyl methacrylate doped with rhodamine 6G

Rhodamine 6G has been dissolved in copolymers of 2-HydroxyEthyl MethAcrylate (HEMA) and Methyl MethAcrylate (MMA) and the resulting solid-state solutions have been pumped at 337 nm and 532 nm. Lasing efficiencies similar to those found in ethanol solution have been obtained with a 1:1 vol/vol HEMA: MMA copolymer matrix, and lifetimes of ca. 10 000 (337 nm pumping) and ca. 75 000 (532 nm pumping) pulses at repetition rates up to 15 Hz and 10 Hz, respectively, have been demonstrated.     

基于非线性啁啾光纤光栅实现的色散可调谐

从原理上证明了一种基于非线性啁啾光纤光栅以及光纤光栅的温度特性的色散可调谐方案.实验证明在25.5℃的温度变化范围内,光纤光栅对1550.43nm波长的色散补偿量从759.1ps/nm上升到1659.9ps/nm,色散调谐范围达到900ps/nm,这个方案具有对补偿波长和特定补偿波长所需要的色散补偿量同时进行调谐的特点.     

快速真空紫外光谱诊断在EAST实验的初步应用

为了在EAST装置上开展高参数放电条件下边界杂质辐射的实验研究,发展了真空紫外(VUV)光谱诊断系统。该系统采用了焦距为200mm的Seya-Namioka型VUV光谱仪,并配备了600g·mm^-1凹面全息光栅,所能观测的波长范围为50~700nm,覆盖真空紫外、近紫外和可见光波段。系统在垂直方向的观测范围为Z=-350~350mm。利用该系统开展了EAST边界杂质谱线的实验研究。通过分析CⅣ(154.8nm)杂质和FeⅡ(235nm)的谱线强度的时间演化行为,验证了该系统谱线强度测量的准确性与可靠性。通过分析CⅠ(365.2nm)杂质辐射强度在加热功率调制下的时间演化行为,验证了该系统研究较短时间尺度的杂质辐射行为的可行性。